Field of the Invention
The present invention relates generally to a volatile organic compounds processing system, and more particularly to a processing system utilizing rotors and an incinerator.
Description of the Prior Art
Organic Solvents are commonly used in many fields. Some organic solvents tend to evaporate from the liquid form and enter the surrounding air and are thus known as “Volatile Organic Compounds”, hereinafter referred to as “VOCs”. Many VOCs have biotoxicity and must be processed before emitting to the atmosphere.
A common way to process the VOCs is the utilization of incinerators to incinerate the VOCs. To treat exhaust air containing low concentrations of VOCs, an adsorption-desorption rotor is usually used to concentrate the VOCs. The existing high efficiency rotor can usually reach a VOCs processing efficiency of 90-95%, with a concentration ratio of 10-25, i.e. the concentration of VOCs in the desorption air is 10-25 times that in the exhaust air. The desorption air is then sent through the incinerator. Even though the existing incinerator can reach a VOCs processing efficiency of 95-99%, the exhaust end of the incinerator still contains some VOCs due to the high concentration ratio of 10-25 in the desorption air.
Owing to the fact that the environmental regulations and the emission standards become stricter and stricter, the existing exhaust air processing systems cannot entirely meet the reduction standards in Air Pollutants Total Control Plan. Therefore, it is of deep concern for the persons skilled in this art to find a solution to increase the processing efficiency of the VOCs processing system.
On the other hand, the airstream expelled from the exhaust end of the conventional incinerator still contains low concentrations of VOCs. Pollutants such as NOx, SOx or suspended solids may also be generated. Air Quality Monitoring Data has shown that the particulate matters are gradually replaced by the pollutants including VOCs, NOx, SOx and suspended solids as the primary source which contributes to Pollutant Standards Index. VOCs, NOx, SOx and suspended solids are also on the reduction standard lists in Air Pollutants Total Control Plan. Therefore, there is a need to strictly reduce the emission of VOCs, NOx, SOx and suspended solids.
To process VOCs, a Taiwanese utility module numbered M444870, hereinafter referred to as “M444870”, discloses a VOCs Secondary Concentration System. FIG. 1 of M444870 shows a conventional method using incinerator to process the desorption air expelled from the rotor. To mitigate its defects, a second rotor as shown in FIG. 2 of M444870 or more rotors as shown in FIG. 4 thereof can be utilized to further process the desorption air expelled from the first rotor, while the desorption air expelled from the second rotor is still processed by an incinerator, which is not shown in the figure. However, the VOCs processing efficiency of a rotor is usually lower than that of an incinerator. Despite that M444870 attempts to replace the incinerator with the additional rotor(s) to process the desorption air expelled from the first rotor, the nature of the lower VOCs processing efficiency of the additional rotor(s) makes the concentration of VOCs in the processed air even higher than what it would be in the method as disclosed in FIG. 1 of M444870. As a result, M444870 builds up higher equipment cost by installed additional rotor(s), and yet the concentration of VOCs in the processed air is not lowered but increased.